This invention relates to optical fiber couplings and, in particular, to fiber splices and connectors of the type in which watch bearing jewels are employed to align two fibers to be coupled.
Optical fiber connectors or splices of the type in which one or more watch bearing jewels are employed to align a pair of fibers are increasingly in common use in the construction of fiber optic transmission systems. A well known problem with such connectors or splices, when used with plastic coated, clad silica fibers, is the phenomenon of "growing out" of the fiber ends. After the fiber end has been stripped of its coating and fitted to the connector or splice, the coating immediately adjacent the fiber end tends to relax and force the fiber end further into the connector. Such movement of the fiber can cause damage to the fiber end and/or the connector itself.
We have previously designed a termination for a plastic coated optical fiber having a bared end portion. The termination includes a body having a cylindrical outer reference surface, a coaxial inner bore for receiving the coated fiber and alignment means for locating the fiber end coaxial with the inner bore. A transparent flat protection window is arranged adjacent and normal to the fiber end.
The purpose of the window is to protect the fiber end from damage when coupling to a similar connector member. The window introduces only a relatively small coupling loss.
In certain applications it is advantageous to reduce even the small coupling loss introduced by such a protection window to a minimum. This may be done by reducing the thickness of the window so that, when the connector member is mated with a similar member, the two fibers being coupled are virtually in contact, being separated only by two very thin windows. However, it has been found that such reduced thickness windows are fragile and tend to be fractured by the fiber itself which, when "growing out" occurs, exerts a considerable pressure on the window.